A. Field of the Invention
The present invention relates to means for propelling a flexible borescope. More particularly, the invention relates to a method and apparatus for propelling, and steering from a remote location, the head of a fiber-optic borescope.
B. Discussion of Background Art
Borescopes are elongated optical devices capable of transmitting visual images to a remote observer. The devices are used to transmit images of objects near the distant end of the device to an observer at the near end of the device. This permits the observer to perform a visual inspection of remote objects within the field of view of the far end of the device. The original devices were used to inspect the bores of guns, hence the name. Presently borescopes are used to facilitate inspection of a large variety of objects located in remote, inaccessible or hazardous areas. Thus, they are used in such diverse applications as the inspection of turbine engines, human bodies, and nuclear reactors.
The first borescopes were essentially elongated tubular microscopes which employed a series of lenses to convey an image of an object in the field of view of a field lens at a remote end of the tube to an objective lens at the observer's end of the tube. Usually, means were also provided to illuminate the field of view of the borescope, as for example by a small lamp located near the remote end of the tube.
Modern borescopes utilize flexible fiber-optic cables rather than lenses. The fiber-optic cables contain parallel bundles of fine transparent fibers, and transmit to one end of the cable an image of the area within the field of view of the opposite end of the cable.
Most fiber-optic borescopes have a flexible protective sheath covering the entire length of the cable. Typically, the sheath is made of a durable, abrasive resistant material such as woven metal. Also, most fiber-optic borescopes include within the sheath a second fiber-optic cable which is illuminated by a bright light source at the observer's end. The second cable transmits light to the remote end of the cable, which then illuminates the field of view of the imaging fiber-optic cable.
A relatively recent improvement in fiber-optic borescopes permits the observer at the viewing end of the borescope to remotely manipulate the distant end of the cable to position the axis of the imaging fiber-optic cable at a desired orientation, thereby bringing into its field of view a desired area of interest. These remotely manipulateable fiber-optic borescopes are referred to as articulated, articulating or articulateable borescopes. By applying tension to one or more flexible wires strung through the protective sheath and attached to a pivotable member near the remote end or head of the cable, the head may be tilted at an angle to the longitudinal axis of the cable. Such borescopes can have either one or two planes of articulation. The latter type permits aiming the head of the borescope to any point in a forward directed hemisphere (or larger portion of a sphere) centered around the head end of the cable. Siegmund, in U.S. Pat. No. 4,290,421, Sept. 22, 1981, discloses such an articulateable borescope.
Borescopes with articulated heads are somewhat easier to push through, or "snake" through, serpentine passageways in a structure being inspected. However, it is an extremely difficult, time consuming operation to thread even a borescope having two planes of articulation through a cluttered, labyrinthine series of passageways, such as those encountered in a jet turbine engine. Also, repeated pushing flexes the fiber optic bundle within the borescope cable and causes fiber damage which substantially shortens the life of the borescope. Moreover, the present methods of threading borescope cables to a desired inspection area require that the cable be in contact with a confining surface, such as a floor section of, or a tubular sheath within, the area to be inspected. Thus, present borescopes do not have the capability of being propelled to an arbitrary point in three dimensional space.
Difficulties are also encountered in pushing a borescope head through passages of a body to examine body organs.
Borescopes used to remotely inspect body organs such as the bowel or bladder are referred to as endoscopes. Sheldon, in U.S. Pat. No. 3,279,460, Oct. 13, 1966, discloses an endoscope construction modification which facilitates forward movement of the endoscope within passages of a human or animal body. He states that flexible endoscopes, or intrascopes, as he refers to them, were found to coil easily in the passages of the body, or to get stuck at the sharp angulations of the examined part or passages. The construction modification described comprises the addition of an inflatable, perforated pouch to be outer wall of the endoscope housing. A hollow, flexible tube connects the pouch to a controllable air supply outside of the body. Inflating the pouch causes it to expand against surbody rounding organ fluids and/or tissues, producing a clearance space for forward movement of the endoscope. Deflation of the pouch effected by air escaping through the perforated front wall of the pouch allows the fluids and/or tissues to relax to their normal unstressed position. Thus the endoscope may be propelled forward against the normally encountered resistance of the fluids and organ tissues by an intermittent wavelike motion somewhat like the peristaltic waves of a normal functioning intestine.
The present invention was conceived of primarily to overcome difficulties typically encountered in remotely propelling and guiding a borescope head to desired inspection locations within engines and structures which are relatively inaccessible. Accordingly, the present invention, although being adaptable to propelling and guiding endoscopes, does not require the cooperative interaction of the passageways through which the apparatus travels for its effective operation. Therefore, the present invention is useful for propelling and guiding borescope heads in a broad range of applications requiring inspection of inaccessible areas.